It's been broken at least since Tails was based on Wheezy. Some of the breakage was fixed in Tails 1.6, but even so it was still broken and the logic on which it is based does not work anymore on Jessie (#8328#note-5).
Given this history, reintroducing this mechanism should come with at least minimal automatic tests.
Remove the restricted network detector.
As explained on https://labs.riseup.net/code/issues/8328#note-5, it's
been broken for 16 months, it is still broken after the partial fix that
went in Tails 1.6, and the logic on which the detector is based cannot
work anymore. Reintroducing and porting this feature is now tracked